diff --git a/include/faabric/util/system_metrics.h b/include/faabric/util/system_metrics.h
index 8b0ba1062..06aa4399e 100644
--- a/include/faabric/util/system_metrics.h
+++ b/include/faabric/util/system_metrics.h
@@ -31,5 +31,5 @@ namespace faabric::util {
 
     UtilisationStats getSystemUtilisation();
     CPUStats getCPUUtilisation();
-    MemStats getMemoryUtilisation();
+    double getMemoryUtilisation();
 }
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